A standalone Gamma World game using the Alternity system. From the back of the book:

"Eight hundred years ago, everything went to hell. Cities vanished, forests burned, and an entire civilization died in nuclear fire, gengineered plagues, and mutagenic poisons.

"Gamma Terra is what's left, a world blighted by radioactive deserts, deadly ruins, and thousands of new and dangerous species armed and armored with bizarre mutations and the wreckage of technology. Humanity is no longer the master of the world.

"Strap on your sword and ready your blaster - it's time to brave the wild frontiers!"